Schizophrenia is a devastating illness, with unknown pathophysiology, that affects 1% of the world's population. The experiments in the following revised proposal will focus on the basal ganglia and dopamine (DA) pathology in schizophrenia (SA1) and relate these changes to those occurring in rats treated with antipsychotic drugs (APDs) (SA2). Our preliminary data shows abnormalities in morphology of DAergic neurons in the substantia nigra (SN) and in the number of TH+ striatal synapses in electron microscopic (EM) studies of postmortem tissue from subjects with schizophrenia (SZ), similar structural changes and a decrease in number of TH+ cells in rats treated with APD. SA1 tests the hypothesis that the DA system is perturbed in the basal ganglia of SZ, using tissue from normal controls, SZ treated with typical or atypical APDs or off-drug. SA2 tests the hypothesis that anatomical changes observed in SN and ventral tegmental area (VTA) of SZ are the results, in part, of APDs, and will determine the contributing physiological mechanisms. In both aims, we will determine if the morphological alterations seen will show regional variations that are consistent with the differential effects of typical and atypical APDs on the activity of midbrain DA neurons. In this revision, we have modified the EM analysis of the SN and added 3 parallel experiments in both the human tissue and rats (treated with haloperidol or clozapine or controls). In SA1a the synaptic organization of DA labeled profiles will be analyzed in the human striatum at the EM level. In SA1b & SA2a, the number and size of Nissl stained, and TH+ cells double labeled with the DA transporter (DAT), or a selective marker of DA cells, SK3, will be determined using stereological methods in the SN/VTA. In SA1c & SA2b at the EM level, the integrity of subcellular organelles and the synaptic organization to the TH+ neurons (also labeled with DAT or SK3) will be studied. Using in situ hybridization SA1d & SA2e will determine if TH synthesis is affected at the level of transcription. SA1c & SA2d will determine if cytoskeletal proteins are upregulated. SA1f & SA2e will determine if the loss of TH in neurons is due to changes at the translational level by using Western blot analysis. SA2f will study the time course of the anatomical changes observed during APD treatment and relate these changes to the development of depolarization (DP) block. SA2g tests the hypothesis that morphological alterations in SN/VTA neurons will not occur in rats treated with APD if DP block is prevented (with a unilateral striatal lesion).